Wall structures formed from a plurality of interconnected, prefabricated and portable panels are used extensively in commercial and industrial buildings for dividing interior regions into smaller work regions. Such structures have proven particularly effective in providing greater privacy within the building, and at the same time improving the interior appearance. For this purpose, the panels are provided with many different exterior finishes, such as colored plastics, carpets and fabrics. Some of these panels also tend to minimize noise, particularly when they are provided with soft exterior finishes, such as by being covered with carpeting or fabric. Many panels of this type are also provided with slotted rails extending vertically along the edges thereof, whereupon fixtures such as desks, shelves, filing cabinets and the like can be mounted on the panels. Due to the desire to mount these fixtures on the panels, the panels thus must be provided with substantial strength and, accordingly, are normally provided with a relatively strong and rigid core so as to provide the necessary strength.
While panels of the above type do tend to minimize noise, nevertheless any noise absorption capability of the panel is normally provided solely by the outer coverings. Further, since these panels are normally of a height substantially less than the floor-to-ceiling height, this also permits the transmission of substantial noise over the panel which, when coupled with the inability of these panels to absorb a high percentage of sound at various frequencies, thus results in these panels being totally unacceptable for use in situations where a high noise reduction and absorption by the panel is necessary. Because of this inability to absorb a high percentage of the sound in the environment, these known panels have conventionally been referred to as non-acoustical-type panels.
In an attempt to provide a panel capable of absorbing a high percentage of directed sound at various frequencies, there are known several so-called "acoustical-type" panels which are more effective in absorbing the environmental noises surrounding the panels. However, to achieve this noise absorption capability, these panels normally comprise a fiberglass core with fabric coverings thereover, the core being surrounded by a rectangular frame which constitutes the sole structure for providing the panel with structural strength. These panels, due to the lack of any structural strength in the core, do not possess the strength and rigidity necessary to permit fixtures such as shelves and the like to be hung thereon. Further, these known acoustical panels possess limited durability and are easily damaged due to the softness and lack of strength possessed by the core of the panel.
In recognition of the need for an acoustical panel, the American Society of Testing Materials (ASTM) has defined an industry standard for testing the sound absorption quality of movable partitions, which standard is defined in ASTM regulation C423-66. This regulation requires that a panel or partition be tested at sound wave frequencies of 250, 500, 1000 and 2000 cycles per second. The panel is rated on a scale of from 0 to 100, and the greater the sound absorption capability of the panel, the higher the numerical rating. This numerical rating, which is normally referred to as the Noise Reduction Coefficient (NRC), is averaged over the four test frequencies set forth above. At the present time, the known carpeted panels which are capable of having fixtures hung thereon normally have an NRC in the range of 30 to 45, whereas the known acoustical panels which utilize a core constructed totally of fiberglass are relatively weak and unstable, and often do not permit fixtures and the like to be hung thereon.
Accordingly, it is an object of the present invention to provide an improved movable panel or partition of the acoustical type for absorbing a larger degree of directed sound at various frequencies, while additionally possessing substantial strength to enable fixtures to be hung thereon. More specifically, it is an object of the present invention to provide:
1. An improved acoustical wall panel, as aforesaid, which can be incorporated into a wall structure and which possesses a relatively high noise reduction coefficient (NRC), such as at least 65 or above.
2. A panel, as aforesaid, which utilizes a core structure capable of absorbing sound with a high degree of efficiency while still providing the panel with substantial strength, stability and rigidity to permit fixtures to be mounted on the panel, as by being hung thereon.
3. A panel, as aforesaid, which possesses substantial strength and durability while at the same time possessing a high noise reduction coefficient.
4. A panel, as aforesaid, which utilizes stressed skins associated with the core for providing the panel with desired strength and rigidity while at the same time permitting the panel to have a high sound absorption efficiency.
5. A panel, as aforesaid, which utilizes the Helmholtz resonator principle for absorbing sound at desired frequencies.
6. A panel, as aforesaid, wherein the core is constructed from a honeycomb structure which defines a plurality of cells, which cells are covered by the stressed skins, and which skins have small openings therein for communication with the cells to thereby define Helmholtz resonators for absorbing sound waves at varying frequencies.
7. A panel, as aforesaid, wherein the core of the panel preferably includes chambers of several sizes so as to create several different types of Helmholtz resonators to thereby absorb a wider range of sound frequencies.
8. A panel, as aforesaid, which utilizes a layer of fibrous sound absorbing material, such as fiberglass, positioned over the honeycomb core for absorbing sound waves of different frequencies.
9. A panel, as aforesaid, which can be manufactured in an economical manner utilizing materials of somewhat conventional construction, which possesses the structural characteristics of prior panels having relatively low sound absorbing capacity, which possesses all of the capabilities of the prior known acoustical panels, and which results in a substantially higher sound absorbing capability than was previously possible with panels of this general type.
Other objects and purposes of the present invention will be apparent upon reading the following specification and inspecting the accompanying drawings.